i am working in visual studio in .net i also facing this issue but it resolved now. the issue is when i run my project is already have a instance create in task manager so i have take below step to resolve the issue

1. close visual studio
2. open task manage -> close the visual studio service (if any)
3. Run the following command in Command Prompt or PowerShell to find and terminate the process: tasklist | findstr Api_name
4. open visual studio
5. clean solution
6. Rebuild S
7. Rebuild Solution

olution Done.